Searchlights are most often employed in installations that require a control mechanism so that an operator can move the searchlight over an area to be searched or aim it at a specific object. A suitable control system must be able to allow positioning the searchlight horizontally (azimuth) and vertically (elevation). For example, in the marine field tugs pushing or towing barges such as on the Mississippi River need searchlights that the operator can control in azimuth in order to sweep from bank to bank across the river and also control in elevation so as to be able to sweep at various distances from the boat.
We are aware of three mechanical systems presently in use for controlling the positioning of a searchlight:
(1) Lever control--a single lever is connected to an inner push rod that can be moved up or down vertically to control elevation of the light and also connected to an outer tubular shaft that can be rotated in order to turn the searchlight in azimuth. PA1 (2) Lever-gear control--a single lever at one end of the control assembly is connected through bevel gears to an inner shaft having a pinion gear on its opposite end which meshes with a curved rack externally attached to the searchlight; elevation of the light is controlled by twisting the lever. The lever is also connected to an outer tubular shaft to rotate the light in azimuth, as in the lever control system. PA1 (3) Wheel-control--two hand wheels are incorporated in the control mechanism. One wheel controls the vertical positioning of the searchlight through the pinion and curved rack arrangement described above for the lever-gear control system. The other wheel rotates an outer shaft for horizontal positioning of the light as in both the lever and lever-gear control systems described above.
Searchlights with one or the other of the above control systems have been sold for many years by several companies that are well-established in this field, including for example, The Carlyle & Finch Co., Perko Inc. and ITT Jabsco Products. The impetus for the present invention is our conviction that the commercially-available searchlights can be improved upon with respect to their control systems in such manner as to provide significant advantages to the manufacturer, distributors and users of the searchlights, and we therefore developed the new design that is the subject of this invention. A principal object of this invention was to provide a new searchlight control mechanism that will allow azimuth and elevational positioning of the light.
One of the problems we became aware of during the course of our research in connection with this invention was that the available searchlights were limited to one or the other of the above three control mechanisms. That is, a searchlight that was purchased with a lever control system could not later be converted to either a lever-gear or double wheel control system without substantial expense, so that any such conversion was impractical. This meant that the purchaser of a searchlight had to make an early choice of one of the three control mechanisms. If, for example, a new operator was selected for a boat at a later date who preferred a different control system, the only solution was to replace the entire light with a different searchlight. Also, a manufacturer had to build an inventory of searchlights with all three control systems if it wanted to be able to fill orders quickly, or else construct a light only after receiving an order which would often result in long delays of shipment to the customer. Therefore, another object of our present invention was to provide a searchlight in which the three types of control mechanisms were readily interchangeable with one another, most usefully interchangeable in the field (i.e. after having been installed on a ship or other environment), to thereby eliminate the problems of changing the control mechanism after the initial installation and reducing manufacturer and distributor problems with respect to inventories.
Another problem we found with the commercially-available searchlights is that the lever-gear and wheel control systems described above both require a pinion and a curved rack to be mounted outdoors inasmuch as the rack is attached to the searchlight housing and the pinion must mesh with the rack. This subjects these gear elements to adverse weather conditions, such as ice or snow accumulation, as well as potential damage by being struck with an object. Also, maintenance and adjustment are more difficult due to the outdoor location of these parts. Accordingly, another main object of our present invention was to devise a control mechanism for a searchlight that can include either a lever-gear type of control or a wheel type of control but which does not utilize an exteriorly mounted rack or pinion; a related feature was to develop a design in which the elements were protected from the weather and easily available for inspection and maintenance.
Another problem we noted with the commercially-available searchlights is the difficulty of customizing the units with respect to the lengths of the shafts employed for the control systems. For example, a searchlight will customarily be mounted on top of a cabin roof or other ship superstructure and have control shafts extending into the interior to position the levers or wheels at a convenient height so that an operator can easily handle the controls. This in turn means that the control shafts associated with the light will need to be available in varying lengths in order to be adapted or customized to a specific installation. The inner shaft of a searchlight incorporating either the lever, lever-gear or wheel control system has typically been a single solid shaft of a customized length chosen to position the controls at the appropriate height. Also, the outer tubular shaft in these control mechanisms is a single piece of tubing of the length required for the selected height. This causes problems for the manufacturer because it is not practical to maintain an inventory of these shafts in all the possible lengths that specific customers may require. The inventory problem also adversely affects the distributors and installers of the searchlights. Moreover, the user of the equipment has a disadvantage in that he cannot change the length of these shafts after the initial installation, so that a new operator who may require a different height for the controls than the first operator cannot be readily accommodated. Thus, another main object of our present invention was to provide a control mechanism for searchlights that would allow facile adjustment of the length of the control shafts by the manufacturer, installer or user, as well as in the field after the initial installation.
In addition to the foregoing objectives, we have also sought to provide other useful objectives during the course of our research and development in connection with the new searchlight system about to be described: a control system with low friction so as to thereby permit easy adjustment of the positioning of the searchlight; a control system that would be self-locking in elevation to thereby facilitate positioning of the light and eliminate the need for a lock to prevent movement of the light because of vibration, pitching of a boat, etc; a control system that was relatively simple in design so as to provide a reliable unit without undue cost; a control system that incorporated fine control of the positioning of the light; and a control mechanism having low wear and with critical elements enclosed and lubricated so as to be relatively simple to maintain and repair. These and other objects will become apparent from the description which follows.